Matt McSpadden wrote:I've enjoyed reading the different opinions on this question, but personally it has created more questions that I would want to ask.
I can promise you that no forest you see on the east coast especially, and almost anywhere else in the world that isn't too remote for people to get to, is natural. It's all been cut down repeatedly for timber and to make room for European agriculture. The reason you see monocultures of pine is because that's the most valued as cheap lumber. Hardwoods are certainly harvested and used for lumber when they appear as "weeds" in a timber stand, and are quite valuable. The oaks that were taken off of the land here when the owner had it clear cut sold for $50,000 apiece, and a truck with 3 logs on it required it's own security detail because it was worth so much. But did the foresters replant any of these high value trees? No. Because they're too messy to manage, too slow growing, and not guaranteed to grow into a useable shape. Doug fir grows tall, fast, and straight, so they replant a monoculture of that. Other species are weeds that they're only happy about if they happen to find them at a useable size when they give to harvest the conifers. Anything that isn't a issue l useable size or shape is cut down and burned to "get it out of that way."
But this experiment in monocultural timber is failing. Japan's monocultural conifers are dying. Scandinavia's monocultural conifers are dying. Even here, disease is starting to spread amongst the Doug firs because there's nothing to stop it. And recent research has discovered that these monocultural timber stands transpire so much
water in the 20 years before they're harvested that they're actively draining the groundwater that literally everything depends on to live.
But even before the insanity of European land management hit these shores, hardly any of the forests were natural. Modeled on natural ecosystems, sure, but they were heavily managed by the nations that existed here for food and resource production. Desirable species were encouraged and protected, and undesirable species were discouraged.
So to point at any forest in the U.S., with the possible exception of the remotest parts of the Olympic peninsula, as an example of what's natural is objective lunacy.
And to understand the role of soil microbiology hardly takes a lifetime. We have great educators that are passionate about the field who can teach you a fairly comprehensive fundamentals course in about an hour. In 8 to 12 hours you can absorb most of what there is to know as a non-researcher.
Case in point, yes, your clover is in a polyculture if it's only 2 feet across... unless you've sprayed herbicide on everything beyond that 2 feet. The confirmed benefits of polyculture stem from the ability of the plants to exchange nutrients and rhizospheric/endophytic microbes with dissimilar plants. Barring an allelopathic response, the benefit is derived from the plants
roots touching, or being close
enough to be bridged by mycelial networks. Most of the disease resistance, pest resistance, drought resistance we observe in plants we now know has little to do with the plant itself and more to do with the microbes it associates with. Each kind of plant produces different exudates which
feed different populations of bacteria, and the combinations of exudates from different types of plants feed a more diverse set of microbes that either could on it's own (and creates soil at a greater depth than a monoculture, as shown in the Jena experiment.)
One of the best examples we have of how this works is with drought resistance. A root crop might associate with a particular bacterium that an herb doesn't, but if the herb is growing in close proximity to that root crop, it can release a chemical signal to recruit that bacterium. In exchange for feeding and housing that bacterium, it induces physiological changes in the herb, including cell wall thickening, which happens to be a key strategy in preventing moisture loss in the face of drought.
And back to the subject of conifers, we now know that there's an important relationship between conifers and hardwoods. Hardwoods have vastly superior photosynthetic capacity... when they have leaves. So much photosynthetic capacity that they end up producing far more carbohydrates than they could ever use. So, in a healthy system, what do they do? They share some of that surplus with the lagging conifers to keep them growing healthy and strong. And what do they get out of it? In the fall and winter, when the hardwoods can't photosynthesize at all, the conifers return the favor.
If industrial farms operating over thousands of acres see a cost benefit to growing a polyculture, then management is hardly an issue at the home scale. It's just a question of what plants, layout, and management style works for the grower. It's still more common to see complex polycyltures being used as cover crops on a large scale, but simpler combinations of plants are finding value amongst large scale commercial food and ethanol producers. Those producers are growing soybeans in the row with their corn crop. They aren't harvesting those soybeans, or tilling them in for
organic matter. They're growing them with their corn because just the presence of soybeans eliminates their need for nitrogen fertilizer at a significant cost savings.